Mixing apparatus for powdered nuclear fuel

ABSTRACT

An apparatus for mixing powdered nuclear fuel is provided in which the mixing space is in the form of a hollow cylinder whereby the inner diameter of the hollow cylinder is larger than half the outer diameter.

-4 1 June 27, 1972 [54] MIXING APPARATUS FOR POWDERED References Cited NUCLEAR FUEL [72] Inventor:

Heinrich Beisswenger, Karisruhe, Ger- UNITED STATESPATENTS many [73] Assignee: Aikem Alpha-Chemie und-Metaliurgie Hume,

Lwpddshafem Germany 3,367,126 2/1968 Howell....................... Oct. 3, 1969 [22] Filed:

Primary Examiner-Wiiliam I. Price Attorney-Cushman, Darby & Cushman [211 App]. No.:

ABSTRACT I 30] Foreign Application Priority Data 1 0C!- 5, 1968 Germany l8 ()1 414.7 An apparatus for mixing powdered nuclear fuel is provided in which the mixing space is in the form of a hollow cylinder whereby the inner diameter of the hollow cylinder is larger than half the outer diameter.

259/50, 51, 109, 1 10, l 9 Claims, 2 Drawing Figures [52] US. [51] Int. Cl. [58] Field ofSearch.......................

MIXING APPARATUS FOR POWDEREI) NUCLEAR FUEL In the nuclear fuel industry, there is the problem of mixing to a uniform product the starting material supplied which is delivered in small units with different isotope composition and frequently also with different technological properties. The mixing is suitably undertaken as a powdery material. The material to be mixed should therefore occur in this form at the start.

With plutonium and also with enriched uranium there is the problem of so shaping the equipment that it is criticality safe. This results in that of the known mixing apparatuses only those with relatively small containers or in the form of elongated cylinders with a relatively small diameter can be used.

Since in general an analysis is performed on each lot which becomes mixed as a unit, it is most economical to work with the greatest possible uniformity of mixing. A mixer in the form of an elongated cylinder permits thereby greater uniformity of mixing than a shorter cylinder. With increasing length, however, the cylinder becomes unwieldy and finally uneconomical. If, for example, the mixer should contain a volume of 50 liters its length amounts to approximately meters, with still longer mixers there is the risk that complete intennixing in longitudinal direction will no longer occur.

It has now been found that the disadvantages of known mixing apparatuses can be avoided if the mixing chamber has the form of a hollow cylinder in which the inner diameter of this hollow cylinder is greater than half the outer diameter and is smaller than the outer diameter minus 40 mm. A construction of this type poses on the one hand a large mixing volume and on the other hand is criticality safe and technically easily realizable.

The invention will be understood best in connection with the drawings wherein:

FIG. 1 of the drawings is a sectional view of a mixing apparatus constructed according to the invention; and

FIG. 2 is a sectional view of a modified form of the invention.

Referring more specifically to the drawing, the apparatus comprises a relatively thin cylindrical shell 1 as the outer wall. Inside this outer shell 1, lies a cylindrical inner wall 2 which is provided with plowshare-like scoops 3 and is rotatable around an axle 4. To reduce expense of material and mass force, it is preferably built as a hollow cylinder as shown. The addition of the materials to be mixed takes place through a nozzle 5 which is able to be closed opposite the mixing chamber 7 by a sliding valve. Instead of the sliding valve 6, there can also be used a trap door which is turnably seated and is formed as a cut out in the cylinder wall. The outer wall I of the mixer can be formed as two half shells l4 and 16 which are able to be dismantled for cleaning. Besides it is suitable to mount the outer wall of the mixer so that it is tumable around the cylinder axis, in order that the material to be mixed can be filled from above and after the mixing can be removed from below.

A typical measurement for a mixing chamber is as follows:

Inner diameter of the mixing chamber 400 mm. Outer diameter of the mixing chamber 480 mm. Length of the mixing chamber 1.5 meter Volume of the mixing chamber 80 liter With the apparatus of the invention a criticality safe mixing of relatively large amounts of powdered nuclear fuels is carried out in simple manner.

The filling volume can be increased if the inner space between the cylinder shell 2 and the axle 4 contains neutron absorbing material 10. The neutron absorption is then most effective if at the same time neutron moderating material 11, especially hydrogen containing material is present. The moderator and the absorber can either be added mixed with each other or the inner space can be filled with the moderator and can be surrounded on the outside with absorbing material. The absorber can be inserted as a further cylindrical shell 12 inside 2. As shown in FIG. 2, as absorbers cadmium and boron are especially suited. As neutron moderators, there can be used polyethylene and other hydrogen containin materials.

The remaining inner space between the shell 1 and the axle 4 is filled with neutron moderating material 18.

In operating according to the drawings, the inner cylinder 2 rotates in order to aid in mixing. It can be supported on the axle for example by spider 20.

What is claimed is:

1. An apparatus for mixing powdered nuclear fuel comprising a hollow cylindrical mixing chamber having an inner wall and an outer wall, the diameter of the cylinder formed by the inner wall being larger than half the diameter of the cylinder formed by the outer wall, said apparatus containing a central axle and the remaining inner space between the cylinder formed by the inner wall and the axle containinga material selected from the group consisting of strong neutron mode rating material and strong neutron absorbing material.

2. An apparatus according to claim 1 wherein the outer wall of the mixing chamber is formed as a pair of separatable half shells.

3. An apparatus according to claim 1 wherein the outer wall of the mixer is mounted for rotation :around the axis of the cylinder.

4. An apparatus according to claim 1. wherein the outer wall of the mixer is mounted for rotation around the axis of the cylinder.

5. An apparatus according to claim 4 wherein scoops are provided on the inner wall to aid in mixing the powdered nuclear fuel.

6. An apparatus according to claim 1 wherein inside the cylinder formed by the inner wall there is provided a cylindrical shell of strong neutron absorbing material and the remaining inner space between this shell and the axle is filled with neutron moderating material.

7. An apparatus according to claim 5 wherein the outer wall of the mixer is mounted for rotation around the axis of the cylinder.

8. An apparatus according to claim 7 wherein scoops are provided on the inner wall to aid in mixing the powdered nuclear fuel.

9. Apparatus as in claim 1 wherein the space between the axle and the inner wall contains only strong neutron absorbing material. 

1. An apparatus for mixing powdered nuclear fuel comprising a hollow cylindrical mixing chamber having an inner wall and an outer wall, the diameter of the cylinder formed by the inner wall being larger than half the diameter of the cylinder formed by the outer wall, said apparatus containing a central axle and the remaining inner space between the cylinder formed by the inner wall and the axle containing a material selected from the group consisting of strong neutron moderating material and strong neutron absorbing material.
 2. An apparatus according to claim 1 wherein the outer wall of the mixing chamber is formed as a pair of separatable half shells.
 3. An apparatus according to claim 1 wherein the outer wall of the mixer is mounted for rotation around the axis of the cylinder.
 4. An apparatus according to claim 1 wherein the outer wall of the mixer is mounted for rotation around the axis of the cylinder.
 5. An apparatus according to claim 4 wherein scoops are provided on the inner wall to aid in mixing the powdered nuclear fuel.
 6. An apparatus according to claim 1 wherein inside the cylinder formed by the inner wall there is provided a cylindrical shell of strong neutron absorbing material and the remaining inner space between this shell and the axle is filled with neutron moderating material.
 7. An apparatus according to claim 5 wherein the outer wall of the mixer is mounted for rotation around the axis of the cylinder.
 8. An apparatus according to claim 7 wherein scoops are provided on the inner wall to aid in mixing the powdered nuclear fuel.
 9. Apparatus as in claim 1 wherein the space between the axle and the inner wall contains only strong neutron absorbing material. 